"And a star with mass greater than 3 times the Sun's gets crushed into a single point, which we call a black hole"

3 solar masses

The term "black hole"is of recent origins. It was
first informally used in 1967 by John Wheeler to identify collapsed
stars. The terminology "frozen star"and "collapsar"
was used in reference to black holes prior to 1968.

Black holes are theoretical objects of extreme density and
posses gravitational fields so strong that nothing can escape
from them. The black hole concept was pioneered by German astronomer
Karl Schwarzchild based upon Einstein's theory of relativity.
Recently, the existence of black holes was strengthened by the
discovery of an object of approximately 3 billion solar masses
at the center of the galaxy M87.

The current hypothesis is that black holes form from the inward
collapse of a neutron star. Based upon this premise, black holes
are brought into being when a neutron star's mass exceeds a certain
critical value. Even though there is not a universally accepted
critical value, most technical sources indicate the critical value
is greater than 3.2 solar masses. A neutron star is the apex on
the celestial chain of evolution, and posses no less than 1.5
and no more than 3.2 solar masses. A star less than 1.5 solar
masses is referred to as a white dwarf. Isaac Asimov noted that
the failure of the nuclear force would result in a chain reaction,
leaving nothing remaining to counteract gravitational forces and
the neutron star would remain in an indefinite collapse, with
it's volume steadily approaching zero and it's surface gravity
nearing infinity.

Therefore, in theory, any neutron star whose mass exceeds 3.2
solar masses will collapse and create a black hole. This is due
to the tightly packed neutrons that can no longer withstand the
star's immense gravitational pull and collapse further.